End Groups Of Poly Research Articles

Functionality-type and chemical-composition separation of poly(lactide-co-glycolide) using gradient elution normal-phase liquid chromatography with basic and acidic additives

End groups of poly(Lactide-co-glycolide) (PLGA) play an important role in determining the properties of polymers for use in drug delivery systems. For instance, it has been reported that the encapsulation efficiency in PLGA microspheres varies significantly between ester-terminated and acid-terminated PLGA. More importantly, the in-vivo degradation time of such polymer excipients is influenced by the functional end-group of the copolymer used.The end group distribution in PLGA polymers has been studied using electrospray and matrix-assisted laser-desorption/ionization – high-resolution mass spectrometry. In both cases, the application of these methods is typically limited to PLGA having a molecular weight of up to 4 kDa. 13Carbon-nuclear-magnetic-resonance has also been reported as a method to differentiate and quantify PLGA end groups with a molecular weight up to 136 kDa. However, reported NMR methods take over 12 h per sample, limiting throughput.Cryoprobe NMR can reduce the time required for the process, however such NMR equipment is costly, which makes it unsuitable for the quality control of PLGA.Here, we present a normal-phase liquid chromatography method capable of resolving functionality type distribution (FTD) and, partially, chemical composition distribution (CCD) in commercial PLGA polymers obtained from ring opening polymerization. This method can separate PLGA polymers with a molecular weight of up to 183.0 kDa while also enabling the simultaneous separation of the difference of Lactic acid (LA)/Glycolic acid (GA) ratios.To achieve this, a cross-linked diol column was used with a ternary gradient from HEX to 0.1 % v/v TEA in EA to 0.1 % v/v FA in THF to allow first for the elution of mono-ester terminated PLGA, followed by the di-acid terminated. In addition, a separation of ester-terminated PLGA in the difference of the LA/GA ratio was achieved.This method is expected to aid in understanding the correlation between PLGA's FTD, CCD, and physical properties, facilitating product development and quality control.

End-Groups of Poly(p-phenylene sulfide) Characterized by DNP NMR Spectroscopy

End-Groups of Poly(<i>p</i>-phenylene sulfide) Characterized by DNP NMR Spectroscopy

Folic Acid-Terminated Poly(2-Diethyl Amino Ethyl Methacrylate) Brush-Gated Magnetic Mesoporous Nanoparticles as a Smart Drug Delivery System.

Currently, chemotherapy is an important method for the treatment of various cancers. Nevertheless, it has many limitations, such as poor tumour selectivity and multi-drug resistance. It is necessary to improve this treatment method by incorporating a targeted drug delivery system aimed to reduce side effects and drug resistance. The present work aims to develop pH-sensitive nanocarriers containing magnetic mesoporous silica nanoparticles (MMSNs) coated with pH-responsive polymers for tumour-targeted drug delivery via the folate receptor. 2-Diethyl amino ethyl methacrylate (DEAEMA) was successfully grafted on MMSNs via surface initiated ARGET atom transfer radical polymerization (ATRP), with an average particle size of 180 nm. The end groups of poly (2-(diethylamino)ethyl methacrylate) (PDEAEMA) brushes were converted to amines, followed by a covalent bond with folic acid (FA) as a targeting agent. FA conjugated to the nanoparticle surface was confirmed by X-ray photoelectron spectroscopy (XPS). pH-Responsive behavior of PDEAEMA brushes was investigated by Dynamic Light Scattering (DLS). The nanoparticles average diameters ranged from ca. 350 nm in basic media to ca. 650 in acidic solution. Multifunctional pH-sensitive magnetic mesoporous nanoparticles were loaded with an anti-cancer drug (Doxorubicin) to investigate their capacity and long-circulation time. In a cumulative release pattern, doxorubicin (DOX) release from nano-systems was ca. 20% when the particle exposed to acidic media, compared to ca. 5% in basic media. The nano-systems have excellent biocompatibility and are minimally toxic when exposed to MCF-7, and -MCF-7 ADR cells.

Synthesis and characterization of aba-type block copolymer of poly(ϵ-caproplactone) with poly(ethylene glycol), by mean of activation end groups

ABSTRACTPoly(ϵ-caprolactone)-b-poly(ethylene glycol)-b-poly(ϵ-caprolactone) (PCL-b-PEG-b-PCL) triblock copolymer were synthesized by mean anionic activation of the hydroxyl end groups of poly(ethylene glycol) in presence of diphenylmethylsodium. Copolymers were characterized by SEC, FT-IR and 1H-NMR spectroscopy, TGA and DSC. Size exclusion chromatographic analysis of obtained copolymers indicated incorporation of CL monomer into PEG without formation of PCL homopolymer. Characterization by FT-IR and 1H NMR spectroscopy of the resulting polymeric products, with respect to their structure, end-groups and composition, showed that they are best described as ester-ether-ester triblock copolymers, whose compositions can be adjusted changing the feeding molar ratio of PEG to CL. The thermal stability of triblock copolymers was less that PEG precursor, but higher that PCL homopolymer. Analysis by mean DSC showed that all copolymers were semi-crystalline and their thermal behavior depending on their composition.

Effects of terthiophene as the end-groups in triblock copolymers consisting of poly(fluorene vinylene) and oligo(phenylene vinylene): Time-resolved fluorescence and its anisotropy

Effects of terthiophene (3T) as the end-groups in poly(9,9-di-n-octyl-fluorene-2,7-vinylene)s (PFVs) were studied by means of time-resolved fluorescence and anisotropy techniques. In a terthiophene end-modified triblock copolymer consisting PFV and oligo(phenylene vinylene) (PV, as the middle segment), [(10PFV)2-7PV](3T)2, steady-state fluorescence spectrum shows much intense vibronic bands compared to those of the reference copolymer without terthiophene groups. In contrast, the absorption spectrum of [(10PFV)2-7PV](3T)2 was almost identical to that of the reference copolymer. Fluorescence quantum yield of the 3T end-modified polymer is significantly lower than that of the reference copolymer: ϕf = 0.62 vs 0.83. It was found that fluorescence spectral profile of [(10PFV)2-7PV](3T)2 is time-dependent: As the delay time increases, relative intensities of the higher vibronic bands increase. Time-resolved signals were analyzed by two decay components, 430 ps (shorter wavelength region) and 630 ps (longer wavelength region). On the other hand, fluorescence anisotropy ratios decrease as the monitored wavelength becomes longer. It is highly likely that the terthiophene end-modified copolymer undergoes structural change in the excited state. The longer decay component can be ascribed to a species of which π-system of the excited PFV part is expanded over the end-group after coplanarization of the terthiophene unit upon the excitation.

Modulating Ion Transport and Self-Assembly of Polymer Electrolytes via End-Group Chemistry

We report a rational design of solid-state dry polymer electrolytes with high conductivity, high mechanical strength, and improved cation transference number. Thiol–ene click chemistry provided orthogonal control over the type and number of end groups in poly(styrene-b-ethylene oxide) (PS-b-PEO) block copolymers. This approach permitted the synthesis of PEO chains with reduced crystallinity, reminiscent of PEO oligomers, thereby playing a key role in improving the room temperature conductivity. Intriguingly, the incorporation of diol or dicarboxylic acid end groups in PS-b-PEO produced a well-defined gyroid structure, leading to order of magnitude improvements in the storage modulus. Out of the various samples examined, the electrolytes bearing terminal diol displayed the highest ionic conductivity and a 2-fold increase in lithium transference number. The improvements in performance are attributed to the reduced interchain aggregation and the anion stabilization mediated by the terminal diol group. The fa...

Atmospheric pressure photo-ionization mass spectrometry for the detection of labile end groups in poly(styrene)

Mass spectrometry is a powerful tool for end group determination. Several ionization techniques are available. Unfortunately for labile-end-group-containing polymers and especially for polystyrene, cleavage of the end group may easily occur upon ionization. An alternative ionization method suitable for non-polar polymers is atmospheric pressure photo-ionization (APPI). High-energy photons can eliminate an electron out of certain compounds forming radical cations. Additionally in the presence of halogenated solvents the released electrons can be captured forming chloride ions. Hence, adducts can be seen in the negative mode as well. In order to analyze the end groups in PS prepared by ATRP APPI was applied to minimize elimination. For all PS-Cl samples the existence of Cl-end groups as sole end group could be shown. For PS-Br partial preservation of the end groups were obtained. Hence, APPI-ToF-MS in negative mode has been proven a suitable tool to analyze polymers with labile end groups.

Determination of diethyleneglycol content and number of carboxylic end groups in poly(ethylene terephthalate) fibers using imaging and conventional near infrared spectroscopy

In this work, multivariate empirical models using conventional near infrared (NIR) spectroscopy and hyperspectral images were employed, respectively, to determine and map the diethyleneglycol (DEG) content and the number of carboxylic end groups (TCG) in poly(ethylene terephthalate) fiber samples. NIR spectroscopy is a fast, clean and efficient technique. NIR spectral data were obtained using two conventional spectrometers and a hyperspectral camera. The regression models were built using partial least squares. The models showed satisfactory results for the evaluated parameters, with Root Mean Squared Error of Prediction (RMSEP) values equivalent to repeatability of the reference methods. The distribution maps of the DEG and TCG content in the fibers samples were obtained by using the models built with the average spectra of the images to estimate the pixel content of each species, allowing us to identify areas with high content of these parameters.

Toughening and Compatibilization of Acrylonitrile–Butadiene–Styrene/Poly (Ethylene Terephthalate) Blends Using an Oxazoline-Functionalized Impact Modifier

An oxazoline-functionalized core–shell impact modifier was synthesized between aminoethanol and acrylonitrile/butadiene/styrene high rubber powder. According to the Fourier transform infrared spectroscopy test, the nitrile groups were partially converted into oxazoline groups successfully. The oxazoline-functionalized acrylonitrile/butadiene/styrene high rubber powder was used as an impact modifier for acrylonitrile–butadiene–styrene/poly(ethylene terephthalate) blends. The differential scanning calorimeter and rheological tests demonstrated that poly(ethylene terephthalate) was partially miscible with acrylonitrile–butadiene–styrene, because the oxazoline groups of oxazoline-functionalized acrylonitrile/butadiene/styrene high rubber powder reacted with the end groups of poly(ethylene terephthalate). The results of scanning electron microscopy indicated that the morphology of acrylonitrile–butadiene–styrene/poly(ethylene terephthalate) blends with proper oxazoline-functionalized acrylonitrile/butadiene/styrene high rubber powder content was improved significantly. The best mechanical properties were achieved, When 6 wt% oxazoline-functionalized acrylonitrile/butadiene/styrene high rubber powder was added into acrylonitrile–butadiene–styrene/poly(ethylene terephthalate) blends.

Controlling the end-groups of Poly (3- Hexylthiophene) via Vilsmeier-haack reaction

π-Conjugated oligomeric and polymeric semiconductors have been the focus of intense research over the past few decades as alternatives to inorganic semiconductors for lowcost electronic applications such as organic thinfilm transistors (OTFTs), light-emitting diodes (OLEDs), and photovoltaics (OPVs). These materials enable vapor- or solution-phase fabrication of large-area, lightweight electronic devices and are compatible with plastic substrates for mechanically flexible, conformable, and wearable electronics. In this research, we aim at modification of the H/Br end groups of poly (3-hexylthiophene) to CHO/Br end groups via Vilsmeier-haack reaction using POCl3 and DMF as the catalytic system in toluene medium. The end groups of the obtained polymer were determined via FT-IR spectroscopy and were further confirmed by Maldi-ToF. The result showed that completion of the Vilsmeierhaack reaction was obtained after 24 h at 75 °C.

A Novel Derivatization Reagent in the Determination of the Number of OH End Groups in Poly(ethylene glycol) by Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry.

The potential of a novel derivatization reagent, trifluoroacetic anhydride (TFAA), in determining the number of OH groups in poly(ethylene glycol) (PEG) was investigated by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). The MALDI mass spectra of the products revealed peaks of sodiated derivative cations, whose shift by the respective increments, Δm/z: 96 × number of OH, allowed for the determination of the number of end functional groups with active hydrogens. In the present study, complete acylation of OH groups by TFAA proceeded rapidly, and only required mixing in acetonitrile solvent without purification. As a result, the number of OH end groups of PEG could be determined rapidly.

Determination of Composition of Poly(ethylene-co-propylene) Glycoles at Molecular Level by MALDI Mass Spectrometry Following Preliminary Derivatization

: This article describes the use of derivatization as an efficient method for the determination of the nature of end groups in poly(ethylene-co-propylene) glycols. These data are helpful in calculating their composition at the molecular level with the aid of MALDI mass spectrometry. For derivatization, formylation is shown to be the most suitable. Knowledge of the nature of end groups allows an easy calculation of composition of the copolymers at the molecular level on the basis of MALDI mass spectra of underivatized and derivatized copolymers. It is underlined that derivatization is particularly useful in the investigation of minor components present in the samples.

Efficient Structural Characterization of Poly(Methacrylic Acid) by Activated-Electron Photodetachment Dissociation

Characterization of end-groups in poly(methacrylic acid) (PMAA) was achieved using tandem mass spectrometry after activated-electron photodetachment dissociation (activated-EPD). In this technique, multiply deprotonated PMAA oligomers produced in the negative-ion mode of electrospray ionization were oxidized into radical anions upon electron photodetachment using a 220 nm laser wavelength, and further activated by collision. In contrast to conventional collision induced dissociation of negatively charged PMAA, which mainly consists of multiple dehydration steps, fragmentation of odd-electron species is shown to proceed via a radical-induced decarboxylation, followed by reactions involving backbone bond cleavages, giving rise to product ions containing one or the other oligomer termination. A single radical-induced mechanism accounts for the four main fragment series observed in MS/MS. The relative position of the radical and of the anionic center in distonic precursor ions determines the nature of the reaction products. Experiments performed using PMAA sodium salts allowed us to account for relative abundances of product ions in series obtained from PMAA, revealing that ion stability is ensured by hydrogen bonds within pairs of MAA units.

Preparation and Characterization of Novel Amphiphilic Hydrogels with Covalently Attached Drugs and Fluorescent Markers

This paper describes the synthesis of styrene-based macromonomers with covalently attached model drugs (ibuprofen and naproxen) or fluorescent markers (pyrene) and their incorporation into linear or hyperbranched p-(chloromethyl)styrene copolymers. Alternatively the copolymers were produced by postpolymerization modification of linear or hyperbranched poly[p-(chloromethyl)styrene], PPCMSt, with the same compounds. The incorporation of these copolymers into amphiphilic conetworks was achieved by two methods: Williamson ether synthesis between PPCMSt and poly(ethylene glycol), PEG, with hydroxyl end groups or by nucleophilic substitution between the chloromethyl moieties in PPCMSt and the amine end groups in poly(oxyalkylenediamine), Jeffamine. The dynamic and equilibrium swelling properties were studied on representative Jeffamine hydrogels. The swelling studies showed that the conetworks absorb water quickly and reach equilibrium in 1−2 h, the equilibrium swelling ratio of gels based on linear or hyperbranched copolymer being 181−358% and 244−480%, respectively. Preliminary drug release studies in different aqueous media showed that the release kinetics and the amount of drugs released from hydrogels depend on the physical properties of drugs, the microstructure of polymer network, and the drug−polymer interaction and more particularly on the hydrolysis dynamics of ester linkage between the drug and the polymer matrix.

Molecular properties of conjugates formed by synthetic hydrophilic polymers and sterically hindered phenols

Water-soluble conjugates are prepared via the chemical modification of poly(vinyl alcohol) and poly(ethylene glycol) by antioxidants taken from the family of sterically hindered phenols. The effects of the degree of substitution of conjugates on the dimensions of molecules and their aggregates are studied by viscometry and light scattering in dilute solutions. It is shown that an increase in the amount of antioxidant groups incorporated into the poly(vinyl alcohol) chain leads to a decrease in the dimensions of single conjugate molecules owing to attraction of hydrophobic groups. Poly(ethylene glycol) molecules carrying end groups of sterically hindered phenols form micellar aggregates that are absent in the solution of the initial polymer. The mean number of molecules involved in such an aggregate is 83. It is found that the presence of hydrophobic end groups in poly(ethylene glycol) molecules causes a sharp reduction in the lower critical solution temperature of a solution relative to that of the initial polymer.

Characterisation of end groups in poly(2-hydroxyethyl methacrylate) by means of electrospray ionisation-mass spectrometry/mass spectrometry (ESI-MS/MS)

Poly(2-hydroxyethyl methacrylate) (poly(HEMA)) has been characterised by means of electrospray ionisation-mass spectrometry/mass spectrometry (ESI-MS/MS), in order to evaluate this technique for the generation of end group information. Low energy collision-induced dissociation (CID) data from poly(HEMA) enabled information on both end groups of the polymer chain to be gleaned, in a similar fashion to that proposed previously for other methacrylate polymer systems. Exact-mass CID information was employed to aid the understanding of the dissociation mechanism of the polymer. Some additional fragmentation pathways, compared to other methacrylate polymer systems, are proposed. An example of how software can aid the interpretation of the MS/MS data is also shown.

Derivatization aids in the determination of end groups in poly(alkylene glycol)s by matrix‐assisted laser desorption/ionization mass spectrometry

A method for end-group characterization by matrix-assisted laser desorption/ionization (MALDI) mass spectrometry following preliminary derivatization with N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) and capryloyl chloride is described and applied to poly(alkylene glycol)s. The MALDI mass spectra of the products revealed peaks of sodiated derivative cations, whose shift by the respective increments allowed the determination of the number of end functional groups with active hydrogens. This approach is particularly efficient for the distinction of cyclic and linear dehydration products among minor components.

Dynamic rheological behavior and morphology of poly(trimethylene terephthalate)/poly(ethylene octene) copolymer blends

AbstractThe dynamic rheology and morphology of poly(trimethylene terephthalate) and maleic anhydride grafted poly(ethylene octene) composites were investigated. A specific viscoelastic phenomenon, that is, a second plateau, appeared at low frequencies and exhibited a certain dependence on the content of elastomer particles and the temperature. This phenomenon was attributed to the formation of an aggregation structure of rubber particles. The analyses of the dynamic viscoelastic functions suggested that the heterogeneity of the composites was enhanced as the particle content or temperature increased. The microstructural observation by scanning electron microscopy confirmed that maleic anhydride could react with the end groups of poly(trimethylene terephthalate) to form a stable interfacial layer and result in a smaller dispersed‐phase particle size due to the reduced interface tension. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

The End Group Modification of Phospholipid Polymer Brush Grafted on Ferric Oxide Nanoparticles for Diagnostics

AbstractNanoparticles are widely applied as diagnostic reagents, drug-delivery carriers or bioaffinity beads. In particular, magnetic particles have been widely used in the study of biomedical applications. When we look ahead to the future, it is needed to construct precisely designed surface containing such as high bioaffinity and capability to capture of small amount protein or specific protein among various protein. As a method to construct precisely designed biocompatible polymer surface, atom transfer radical polymerization (ATRP) was widely used as a living free radical polymerization. ATRP has advantages such as control of molecular weight, narrow polydispersivity, easy synthesis of block copolymer, and preparation of high density polymer brush under mild condition. Previously, we have demonstrated synthesis of poly (2-methacryloyloxyethyl phosphorylcholine (MPC)) brush on ferric oxide (Fe3O4) by ATRP from immobilized initiator includes bromine that ATRP moiety. Here, it is known that poly(MPC) has been not affected for reduction of nonspecific binding, salt concentrations, pH and temperature. In this state, the poly(MPC)-grafted Fe3O4 could not be used for diagnostic material and collection material using magnetic interaction because poly(MPC) suppress protein adsorption. To introduce immobilization part for protein, p-nitrophenyloxycarbonyl polyethylene glycol methacrylate (MEONP) monomer that has active ester was polymerized as a block component. The poly(MPC-b-MEONP)-grafted Fe3O4 could capture proteins via active ester to amine of proteins. However, on careful consideration, this immobilization method had disadvantage for capture protein because immobilization part located in the side chain, not locate most outer surface. We focused on bromine (Br) located on end group of poly(MPC) brush, probably locate most outer surface. If the end group would be modified easily, the technique will be most effective modification. We adapted the reduction from azide (N3) to amine (NH2), after Br was exchanged to N3. This reduction has been called “staudinger reduction”. Generally, Click chemistry that reaction between N3 and alkyne is famous as a reaction of N3. On the other hand, the modification technique has wide application range due to amine group. At first, bromine was converted into azide, N3 using NaN3. Furthermore, the N3 was reduced to NH2 using PPh3 and H2O. The purification of magnetic nanoparticles with end group modified poly(MPC) brush was easy because of use of external magnetic interaction. The surface characterization at each step was estimated by XPS and FT-IR spectrum measurement. The absorbance signal attributed to N3 was appeared around 2000 cm-1 from FT-IR spectrum and N1s signal according to NH2 was observed at 399 eV from XPS measurement. The surface NH2 could react to carboxyl group or convert into other functional groups easily. The end group modification will be a useful for various bioaffinity bead applications.

Studies on the Synthesis and the Reaction Mechanism of Epoxy-Terminated Polystyrene Oligomer

The living poly(styryl)lithium was prepared by anionic polymerization with the protection of argon under normal pressure, where styrene, cyclohexane, THF and n-butyllithium were used as monomer, solvent, polar reagent and initiator, respectively. Epoxy-terminated polystyrene oligomers with narrow molecular weight distribution were synthesized by the copolymerization of the end groups of poly(styryl)lithium with glycidyl methacrylate (GMA) at a moderate temperature. The oligomers were characterized using GPC, FT-IR, 1H-NMR, 13C-NMR and Hydrochloric acid-Dioxane Argentimetric method. The effects of GMA dosage, copolymerization duration and temperature on the content of epoxy end group were also studied. The results indicated that the double bond of GMA could polymerize with poly(styryl) carbanion and the content of epoxy end group could be adjusted. It was found that the optimal conditions for the copolymerization were reaction temperature at 10 °C and 2 h for copolymerization duration.